1. Field of the Invention
The present invention relates to a fuel shutoff valve, which is to be installed to or mounted on the fuel tank of vehicle.
2. Description of the Related Art
Within a fuel tank, a fuel shutoff valve is disposed. The fuel shutoff valve not only discharges gases that the evaporating fuel generates, but also shuts off the fuel from flowing out thorough the discharge port of the fuel tank. For example, a conventional fuel shutoff valve 9 is installed to the top of a fuel tank 91, as illustrated in FIG. 10. The conventional fuel shutoff valve 9 comprises a casing 93, and a float 94. The casing 93 is provided with a connector passage 92 on the top. The connector passage 92 is to be connected to a filled-up fuel detector, for instance. The float 94 ascends and descends, depending on a buoyant force that is exerted on it. The buoyant force results from the rise and fall of the liquid-fuel level of fuel that flows into a valve chamber within the casing 93. Moreover, an upper cylinder 95 is put in place above the float 94, and makes the connector passage 92. The ascending float 94 attaches to a seal 96 that is formed at the lower end of the upper cylinder 95. The descending float 94 detaches from the seal 96. When the liquid-fuel level within the valve chamber rises to ascend the float 94, the top wall of the float 94 makes a contact with the seal 96 to shutoff the connector passage 92. On the contrary, when the liquid-fuel level within the valve chamber falls to descend the float 94 as shown in FIG. 11, the top wall of the float 94 separates from the seal 96 to open the connector passage 92. In addition, the float 94 is provided with a claw 97 on the peripheral wall. The claw 97 projects from the peripheral wall, and is then locked to a guide hole 98 ascendably and descendably. The guide hole 98 is opened in the peripheral wall of the casing 93. Thus, the claw 97 ascends and descends while being guided by the guide hole 98. When the claw 97 comes in contact with a lower end 98a of the guide hole 98, the float 94 is inhibited from descending.
However, when the float 94 ascends to come in contact with the seal 96 of the casing 93, and when the float 94 descends to come in contact with the guide hole 98's lower end 98a, the float 94 might produce impact noises. Moreover, the impact noises might be hearable to passengers in the passenger compartment of vehicle.
Accordingly, as disclosed in Japanese Unexamined Patent Publication (KOKAI) Gazette No. 7-35,255 or Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2002-21,665, the bottom of a casing has been heretofore provided with a rubber seat or an elastic arm in order to reduce the impact noises that might be generated when a float comes in contact with the casing.
However, Japanese Unexamined Patent Publication (KOKAI) Gazette No. 7-35,255 and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2002-21,665 only disclose to reduce the impact noises that the descending float might produce, but they do not at all disclose to reduce the impact noises that the ascending float might produce. Moreover, it is required to provide the casing with a floor plate in order to enable the rubber seat or elastic arm to be installed to or mounted on the casing. Consequently, the conventional fuel shutoff valves set forth in the patent publications have come to have complicated structures.